Processes for production of thionyl chloride



. directly in the reactions.

Patented Nov. 7, 1944 PROCESSES FOR.

PRODU CHLOE E I('IlTION OF THIONYL John P. Edwards, Niagara Falls, N. Y., assignor to Hooker. Electrochemical Company,

Niagara Falls, N. Y., a corporation or New York No Drawing. Application Augustll, 1943, Serial No. 498,281

7 Claims.

Heretofore thionyl chloride has been produced by reaction of sulphuric acid or sulphur trioxide with sulphur monochloride and chlorine or with sulphur dichloride. acid with these chlorides of sulphur is as follows:

The reaction of sulphur trioxide with these chlorides of sulphur is as follows:

Reactions (1) and (2) are generally unsatisfactory because of the fact that for every molecule of 8001: two molecules of H01 are roduced. The HCl comes ofi mixed with $02, from which it must be separated, and thereis not always a sumcient demand for this by-product. Sulphur trioxide as such is expensive and Reactions (3) and (4) are commonly carried out by means'of SO: evolved from oleum. As the heat of reaction is considerable and S03 boils at about 45 C., it is reacted in gas phase. In the case 01' Reaction (3) chlorine is passed in at the same time to avoid production of sulfuryl chloride and pyrosuliuryl chloride.

I have now discovered that instead of evolving from oleum for use in the above reactions, the oleum itself may be advantageously used Assuming oleum containing 70 per cent $03, the reactions are as iollows:

80:. Moreover. it will be observed by comparison oi Reactions (1) and (2) with Reactions (5) and (6) that the quantity or lay-product HCl is de-' creased irom a ratio of two molecules oi HCl to one or B0: to a ratio of, one moleculeof HCl to nearly two or 8001:; or, in other words, the molecular proportion of 1101 produced for a given The reaction of sulphuric.

quantity of SOC]: is decreased to a little more than one quarter of that produced in the reaction with sulphuric acid alone, which is the only reaction of the prior art that is practicable for carrying out in liquid phase. Besides the saving in time, improved yield and reduction in by-product HCl, a further practical advantage as compared with the process in which S03 is evolved from the oleum is that no H2804 is left over to be shipped back to the manufacturer of the oleum.

Reactions (5) and (6) are preferably carried out in a glass-lined, jacketed, iron reactor, equipped with an agitator, manometer, thermometer -well exits for SO: and HCland a reflux condenser. There must also be a chlorine inlet tube, which should extend to near the bottom of the reactor. The oleum should have as high a content of $03 as practicable and should preferably be liquid. In order to minimize production of higher oxides of SCls, e. g., sulfuryl and pyrosulfuryl chloride. and afl'ord better control of the reaction, which is otherwise quite violent, the oleum is preferably added gradually to a bodyof the chlorides of sulphur, so that the latter may be in large excess until near the finish of the reaction. The sulphur monochloride or dichloride is therefore first charged into the reactor.

If desired, antimony trichloride may be added to serve as catalyst. With the agitator working and cooling water flowing in the reactor jackets, the oleum is added at such a rate that the temperature is kept below C., and preferably at substantially 25 C. The admission of chlorine may be started at the sametime or later, depending upon whether sulphur monochloride or dichloride is the other reagent. At the' finish it is desirable that there should be a slight excess of both oleum and chlorine in the mixture, over the theoretical quantities.

After the optimum quantities of oleum and chlorine have been added the charge is heated by passing steam through the reactor jacket and refluxed until the refluxing temperaturehas become stabilized at substantially C., which is the boiling point 01' thionyl chloride. The product is then distilled away from residual reagents and high boiling oxides and other impurities and iurther treated in any of the known ways to purityit.

In the foregoing it is to be understood that by "oleum" is meant anhydrous sulphuric acid hav ing dissolved therein a substantially quantity of sulphur trloxide, also commonly known as "tuming sulphuric aci notto be confused with commercial "10o per cent sulphuric acid," which maycent sulphuric acid, to a body of reagent of the.

group consisting of sulphur monochloride, sulphur dichloride and mixtures of the two, with agitation and cooling to maintain the temperature of the reaction mixture at not over 45 C. while venting off the gaseous products, and recovering the thionyl chloride from the resulting liquid reaction mixture.

2. The process for preduction of thionyl chic-- ride, hydrogen chloride and sulphur dioxide which comprises gradually adding free chlorine and oleum, consisting of anhydrous sulphuric acid having dissolved therein not less than one mol of sulphur trioxide per mol of sulphuric acid, to a body of reagent of the group consisting of sulphur monochloride, sulphur dichloride and mixtures of the two, with agitation and cooling to maintain the temperature of the reaction mixture at not over 45 C., while venting, of! the gaseous products, and recovering the thionyl chloride from the resulting liquid reaction mixture.

3. The process for production of thionyl chloride, hydrogen chloride and sulphur dioxide which comprises gradually adding free chlorine and oleum, consisting of anhydrous sulphuric acid having dissolved therein substantially 2.8 mols of sulphur trioxide per mol of sulphuric acid, to a body of reagent of the group consisting of sulphur monochloride, sulphur dichloride and mixtures of the two, with agitation and cooling to maintain the temperature of the reaction mixture at not over 45 C., while venting off the gaseous products, and recovering the thionyl chloride from the resulting liquid reaction mixture.

, 4. The process for production of thionyl chloride, hydrogen chloride and sulphur dioxide which comprises gradually adding free chlorine and oleum, consisting of anhydrous sulphuric acid having dissolved therein sulphur trioxide in amount materially greater than the sulphur trioxide, if any, contained in so-called 100 per cent sulphuric acid, to a body of reagent of the group consisting of sulphur monochloride, sulphur dichloride and mixtures of the two, with agitation and cooling to maintain the temperature of the reaction mixture at substantially 25 C., while venting 011 the gaseous products, and recovering the thionyl chloride from the resulting liquid reaction mixture.

5. The process for production of thionyl chloride, hydrogen chloride and sulphur dioxide which comprises graduallyadding free chlorine and oleum, consisting of anhydrous sulphuric acid having dissolved therein sulphur trioxide in amount materially greater than the sulphur trioxide, if any, contained in so-called "100 per cent sulphuric acid, to a body of reagent of the group consisting of sulphur monochloride, sulphur dichloride and mixtures of the two, with agitation and cooling, while regulating the rate of admission of chlorine and oleum and the cooling to maintain the temperature of the reaction mixture at not over 45 C. and venting of! the gaseous products, and recovering the .thionyl chloride from the resulting liquid reaction mixture.

6. The process for production of thionyl chloride, hydrogen chloride and sulphur dioxide which comprises gradually adding .free chlorine and oleum, consisting of anhydrous sulphuric acid having dissolved therein sulphur trioxide in amount materially greater than the sulphur trioxide, if any, contained in so-called per cent sulphuric acid, to a body of reagent of the group consisting of sulphur monochloride, sulphur dichloride and mixtures of the two, with agitation and cooling to maintain the temperature of the reaction mixture at not over 45 C., and distilling the thionyl chloride from the resulting liquid reaction mixture.

7. The process for production of thionyl chloride, hydrogen chloride and sulphur dioxide which comprises gradually adding free chlorine and oleum, consisting of anhydrous sulphuric acid having dissolved therein sulphur trioxide in amount materially greater than the sulphur trioxide, if any, contained in so-called "100 per cent sulphuric acid, to a body of reagent of the group consisting of sulphur monochloride, sulphur dichloride and mixtures of the two, with agitation and cooling to maintain the temperature of the reaction mixture at not over 45 C., while venting off the gaseous products, until a slight excess of chlorine and oleum for completion of the reaction have been added, raising the liquid reaction mixture to refluxing temperature, continuing the refluxing until the temperature has become stabilized, and recovering the thionyl chloride from the resulting liquid reaction mixture.

- JOHN P. EDWARDS. 

